1. Field of the Invention
The present invention relates to a method of detecting floating mode of a touch panel and more particularly to a method of detecting floating mode of sensing clusters of a capacitive touch panel generated under the floating mode.
2. Description of the Related Art
The touch concept of a capacitive touch panel is an approach detecting positions touched by users according to capacitance variations changed by static electricity on human body. To effectively respond to the signal of static electricity on human body, a metal housing generally used by a capacitive touch panel is connected to a grounding signal of the capacitive touch panel to constitute an electric ground structure so that users' hands are definitely in contact with the capacitive touch panel.
The widespread tablet personal computers (PC) and smart phones with large screens allow users to touch the touch panels of the electronic equipment with fingers or palms only. However, because of the ungrounded nature, irregular capacitance variations of the touch panels arise from the operation of the ungrounded touch panels or a floating mode of the touch panels.
With reference to FIGS. 6A to 6C, when a capacitive touch panel is operated under a grounding mode, a touch event generates an analog sensing signal variation. A value of capacitance variation (dV value) is obtained by subtracting a magnitude of the analog sensing signal from a preset base value of the touch panel and the peak value of the capacitance variation is positive. With reference to FIG. 7A, in a sensing frame 10 with full-frame sensors detecting continuously reporting hexadecimal sensing values, the sensing values of a sensing cluster 11 corresponding to the capacitance variation are shown.
With reference to FIG. 6D, if the touch event takes place under the floating mode, the peak value of the values of capacitance variation (dV value) is negative. With reference to FIG. 7B, in a sensing frame 10 with full-frame sensors detecting continuously reporting hexadecimal sensing values, the sensing values of central sensing points 111 of the sensing cluster 11 are negative, namely −150 and −100 (hexadecimal values). As the coordinates of a touch object are determined by the maximum value of the sensing cluster, the direct impact is incorrectly determined coordinates caused by the irregular capacitance variation.
Hence, the error rate of identifying touch objects increases if capacitive touch panels are operated under the floating mode.